PBX switch incorporating methods and apparatus for automatically detecting call appearance values for each primary directory number on a basic rate interface

ABSTRACT

A PBX switch incorporates methods and apparatus for automatically configuring Call Appearance values in an ISDN BRI. The methods and apparatus include providing means for one PDN to call the other PDN in the same BRI, recording the Call Appearance data for the first call, placing the first call on hold and calling the same number again, recording the Call Appearance data for the second call, and repeating the process until all Call Appearance values have been recorded. According to the invention, the process is repeated for both PDNs in each BRI coupled to the PBX switch.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the Basic rate Interface (BRI) for theIntegrated services Digital Network (ISDN). More particularly, theinvention relates to a PBX switch which incorporates methods andapparatus for automatically detecting call appearance values for eachPrimary Directory Number (PDN) in an ISDN BRI.

2. Brief Description of the Prior Art

The Basic Rate Interface (BRI) of ISDN service consists of two Bchannels, each having a bandwidth of 64 kbits/s and one D channel havinga bandwidth of 16 kbits/s. Generally, each of the B channels can be usedto support one voice connection or one data connection, or the two Bchannels can be used together to support one 128 kbits/s dataconnection. The D channel is used for signaling between the customerequipment (terminal equipment or TE) and the central office in order tosetup, manage, and tear down connections. Each B channel is assigned adirectory number (DN), i.e. a ten digit telephone number.

Two signaling protocols are used with BRI ISDN in order to establish andmaintain connections: The layer 3 Q.931 protocol and the LAPD (linkaccess protocol for the D channel). Q.931 messages are carried within anLAPD frame on the D channel. A Q.931 message includes several octetsspecifying protocol discriminator, length of call reference value, callreference value, message type, etc. Some of the messages sent using theQ.931 protocol include SETUP, SETUP ACKNOWLEDGE, CALL PROCEEDING,CONNECT, CONNECT ACKNOWLEDGE, RELEASE, RELEASE COMPLETE, HOLD, and HOLDACKNOWLEDGE.

The 1999 Version of the Beilcore National ISDN BRI Terminal Equipment(TE) Generic Guidelines (SR-4620, Issue 1, Dec. 1998 specifiesguidelines for implementing many ISDN features. Among these features isa feature known as Call Appearance.

With Call Appearance, a single BRI can respond to up to 128 DNs.Moreover, customer equipment can be designated with up to 128 terminalendpoint identifiers (TEIs) each of which identifies a specifictelephone or device connected to the BRI. Using Call Appearance andTEIs, each of up to 128 telephones or other devices connected to asingle BRI can be provided with a separate DN. Further, each of thetelephones connected to the single BRI can be configured as multilinephones responding to several DNs using electronic key telephone service(EKTS).

EKTS permits a number of illuminated keys on a telephone set to beaddressed by the central office to indicate virtual additional lines.Those skilled in the art will appreciate that regardless of the numberof Call Appearances, the single BRI only supports two active telephonecalls at one time. More calls may be placed on hold at the centraloffice, using Q.931 signaling, but only two calls may be active at onetime.

Separate Call Appearance values (0-63) are assigned to each B channelaccording to the service contract chosen by the customer. As mentionedabove, two DNs are assigned to the BRI. This is the case when both Bchannels have a Call Appearance value of 0. These DNs are referred to asthe primary directory numbers (PDNs). Each PDN may have a CallAppearance value other than 0 (up to 63) associated with it depending onthe customer service contract. The call appearance value indicates thenumber of additional DNs associated with the B channel identified by thePDN.

As mentioned above, the Call Appearance values are in the range 0 to 63for each B channel. The values used and the specific meaning of eachCall Appearance value are defined during the ordering process in anagreement between the customer and the Central Office.

The different values are usually used to handle Central Office features(e.g. call waiting indication, voice mail message, call forwarding) andmultiple calls for same B channel. In addition, choosing a specialarrangement of Call Appearances and directory numbers allows a PBX tooffer the equivalent of Direct Inward Dial capability over standard BRIlines.

Table 1 below illustrates an example of three BRI lines with multipleCall Appearances and shared multiple directory numbers. The maindirectory number for each B channel is italicized.

TABLE 1 Circuit 1 Circuit 2 Circuit 3 CA B1 B2 B1 B2 B1 B2 01 555-4001555-4001 555-4001 555-4001 555-4001 555-4001 02 555-4002 555-4002555-4002 555-4002 555-4002 555-4002 03 555-4003 555-4003 555-4003555-4003 555-4003 555-4003 04 555-4004 555-4004 555-4004 555-4004555-4004 555-4004 05 555-4005 555-4005 555-4005 555-4005 555-4005555-4005 06 555-4006 555-4006 555-4006 555-4006 555-4006 555-4006

Incoming calls for any of the six directory numbers are presented by theCentral Office on all associated channels with the same Call Appearancevalue. In the PBX, each of the Call Appearances is assigned to adifferent station.

According to the state of the art, customer equipment must be manuallyconfigured with a service profile identifier (SPID) as well as thenumber of Call Appearances for each PDN. The correct configuration ofBRI trunks and telephone equipment at the customer's premises requiresspecialized service engineers. The equipment must be configured for CallAppearance Call Handling (CACH) based on documentation provided by thecentral office. The available documentation is often not accurate or notup to date during the installation and (remote) configuration of thetelephone equipment. A wrong configuration could leave trunk interfacesunusable by the customer.

The configuration of customer equipment is even more difficult whenmultiple BRIs are involved. For example, many PBX systems utilizemultiple ISDN BRIs as an alternative to multiple individual DS1 or moreexpensive T1 connections. The Siemens Hicom 150 provides up to 16 BRIsthrough four interface cards, each of which supports four ISDN BRIs.Configuring a Hicom 150 could conceivably require configuring up to2,048 Call Appearances (32*64).

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide methods andapparatus whereby customer equipment can be easily configured for ISDNCall Appearances.

It is also an object of the invention to provide methods and apparatusfor accurately configuring customer equipment for ISDN Call Appearances.

It is another object of the invention to provide methods and apparatusfor configuring customer equipment for ISDN Call Appearances without theaid of a service technician.

It is yet another object of the invention to provide methods andapparatus for quickly configuring customer equipment for ISDN CallAppearances.

It is another object of the invention to provide methods forautomatically configuring call appearance values in a PBX device.

It is still another object of the invention to provide a PBX device withthe capability of self-configuring call appearance values.

In accord with these objects which will be discussed in detail below,the methods according to the invention include generating a call fromone PDN to the other in the same BRI circuit and monitoring the messageexchange on the D channel to obtain Call Appearance information. Thecentral office provides the first valid Call Appearance (via the Dchannel) to the PDN being called and this value is stored in the calledPDN database.

To get all the provided Call Appearance values for each channel, thefirst call is placed on hold. A new call is generated from one PDN tothe other in the same BRI circuit. The central office provides thesecond valid Call Appearance to the PDN being called and this value canalso be stored in the called PDN database. This process is repeated forboth channels as long as the central office offers new Call Appearancevalues.

The method of the invention requires only the use of standard networkprotocol procedures needed for standard call processing. This means thatthe method is not dependent of supplementary BRI services being offeredby the central office that support terminal parameter downloading.

Thus, the method can be implemented in any existing or planned telephoneequipment with no hardware and small software enhancement effort. Themethod is able to provide the Call Appearance values for BRI trunkssupported by the telephone equipment, independent of the central officeto which the customer's premises is connected.

The presently preferred embodiment is based on a modified Hicom 150. Allof the hardware and low level software functionality needed to implementthe inventive method is already available via existent function calls orvia defined mailbox messages at the Device Handler, Database or Loadwarelevel.

The new procedure is preferably located at the Device Handler andactivated when the TMQ4 line card start-up is finished, layer 1 andlayer 2 are up, and TEI and SPID handling are successfully accomplished.However, the methods of the invention can be implemented in virtuallyany ISDN customer equipment whether it be voice equipment or dataequipment.

Combining the methods of the invention with known methods fordetermining the SPID of BRI trunks, a stand-alone test gear to identifyBRI characteristics can be built.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a high level flow diagram of a simple layer 3 message exchangeaccording to the methods of the invention.

FIG. 2 is a high level flow diagram of a more elaborate layer 3 messageexchange according to the methods of the invention.

FIG. 3 is a high level block diagram illustrating an apparatus forperforming the methods of the invention.

FIG. 4 is a high level block diagram of a PBX switch incorporating themethods of the invention.

DETAILED DESCRIPTION

Turning now to FIG. 1, a simple layer 3 message exchange betweencustomer equipment and the central office (CO) is illustrated wherebycall appearance information is obtained during a call from PDN1 to PDN2.A SETUP message is sent to the CO with call reference (CR) equal to 1.The CO responds with a CALL PROCEEDING message with CR=81 and a SETUPmessage with CR=2 and call appearance (CA) equal 1. The call isterminated by the customer equipment sending a RELEASE command withCR=82 and the CO responding with RELEASE COMPLETE with CR=81.

The above message exchange illustrates how CA information is obtainedfrom the CO during a single call. According to the methods of theinvention, multiple calls are made to the same PDN until all CAs areobtained. FIG. 2 illustrates in a simplified manner how this isaccomplished.

In the first three message exchanges in FIG. 2, a call is setup fromPDN1 to PDN2 and the CA=1 is obtained. A CONNECT ACK with CR=2 isreceived when the PDN2 accepts the call. PDN1 then puts the first callon hold with HOLD (CR=1) message and the hold is acknowledged with theHOLD ACK (CR=81) message. Though not illustrated in FIG. 2, the PDN1 nowinitiates a second call to PDN2 which results in a call waiting messageon the PDN2 line together with a CA value which will be stored, assumingthat PDN2 has at least 2 CAs.

Upon receiving the second call, PDN2 places the first call on hold usingthe HOLD (CR=82) message which is acknowledged with the HOLD ACK (CR=2)message. Now that two CAs have been obtained, PDN1 will repeat theprocess putting the latest call on hold and initiating another calluntil PDN2 is unable to accept any more calls, i.e. PDN1 gets a busysignal.

After the process described above is completed with PDN1 calling PDN2,it is repeated with PDN2 calling PDN1. In the case of a PBX such as theHicom 150, the process is repeated for each BRI coupled to the PBX.

As mentioned above, the presently preferred embodiment of the inventionis embodied as software or firmware in the Siemens Hicom 150 PBX device.However, it will be appreciated that the methods of the invention can beembodied in any TE coupled to a BRI. FIG. 3 illustrates a generichardware embodiment of the invention.

Referring now to FIG. 3, the apparatus 10 includes a logic unit 12 whichis coupled to a call appearance database 14, a directory number memory16, the BRI B channels 18, and the BRI D channel(s) 20. The logic causesthe B channels to call one another using the PDN data provided in the DNmemory and monitors the D channel to collect call appearance data whichis stored in the database.

Those skilled in the art will appreciate that the database 14 and thememory 16 may be the same memory device and that the CA data collectedin the database may be forwarded to another part of the TE forappropriate use. It will also be appreciated that the logic may beembodied as a processor with associated program memory, as anApplication Specific Integrated Circuit (ASIC), as a Field ProgrammableGate Array (FPGA), as a state machine, or any other appropriate devicefor carrying out the methods of the invention.

Referring now to FIG. 4, a PBX switch 100 according to the invention isa modified Siemens Hicom 150. The switch 100 includes a plurality oftrunk cards 102, each being coupled to a plurality of ISDN BRI trunklines 104, and plurality of subscriber line boards 106, each beingcoupled to a plurality of subscriber lines 108.

The switch is operated by main software 110 which includes a data base112, a device handler 114, and a call processing switching unit 116. Asmentioned above, all the hardware and low level software functionalityneeded to implement the inventive method is already available in theHicom 150 via existent function calls or via defined mailbox messages atDevice Handler, Database or Loadware level. The new procedure ispreferably located at Device Handler 114 and is activated when the trunkboards start-up is finished, layer 1 and layer 2 are up, TEI and SPIDhandling are successfully accomplished.

As mentioned above, the methods of the invention requires only the useof standard network protocol procedures needed for standard callprocessing. This means that the method is not dependent of supplementaryBRI services being offered by the central office that support terminalparameter downloading. Thus, the method can be implemented in anyexisting or planned telephone equipment with no hardware and smallsoftware enhancement effort. The method is able to provide the CallAppearance values for BRI trunks supported by the telephone equipment,independent of the central office to which the customer's premises isconnected.

Those skilled in the art will appreciate that the methods of theinvention can be combined with known methods for determining the SPID ofBRI trunks to create a stand-alone test gear to identify BRIcharacteristics. However, the primary intention of the invention is toprovide a means whereby telephone equipment coupled to one or more BRIscan be quickly self-configured without the aid of a technician.

There have been described and illustrated herein methods and apparatusfor automatically identifying call appearance values in an ISDN BRI.While particular embodiments of the invention have been described, it isnot intended that the invention be limited thereto, as it is intendedthat the invention be as broad in scope as the art will allow and thatthe specification be read likewise. It will therefore be appreciated bythose skilled in the art that yet other modifications could be made tothe provided invention without deviating from its spirit and scope as soclaimed.

1. A method for automatically identifying Call Appearance values from a message exchange over a D channel in a PBX device coupled to multiple ISDN Basic Rate Interfaces (BRIs), said method, for each BRI coupled to the PBX device, comprising the steps of: (a) generating a first call from a first Primary Directory Number (PDN1) to a second Primary Directory Number (PDN2) within a single BRI circuit; and (b) monitoring the message exchange on the D channel to obtain first Call Appearance information.
 2. A method according to claim 1 further comprising the step of: (c) obtaining said first Call Appearance information from the D channel.
 3. A method according to claim 2 further comprising the steps of: (d) putting the first call on hold; (e) generating a second call from PDN1 to PDN2 in the single BRI circuit; and (f) monitoring the message exchange on the D channel to obtain second Call Appearance information.
 4. A method according to claim 3 further comprising the step of: (g) obtaining said second Call Appearance information from the D channel.
 5. A method according to claim 4 further comprising the step of: (h) repeating the steps of putting a call on hold, generating another call, and monitoring the D channel until the generated call results in a busy signal.
 6. A method according to claim 5 further comprising the step of: (i) repeating steps a-h with calls being generated from PDN2 to PDN1.
 7. A PBX device coupled to multiple ISDN Basic Rate Interfaces (BRIs), said PBX device comprising: (a) dialing means for generating a first call from a first Primary Directory Number (PDN1) to a second Primary Directory Number (PDN1) within a single BRI circuit; and (b) monitoring means for monitoring message exchange on the D channel to automatically obtain first Call Appearance information.
 8. A PBX device according to claim 7 further comprising: (c) capture means for obtaining said first Call Appearance information from the D channel.
 9. A PBX device according to claim 8 further comprising: (d) holding means for putting the first call on hold; and (e) repeating means coupled to said dialing means and said monitoring means, wherein upon putting the first call on hold, the repeating means causes the dialing means to generate a second call from PDN1 to PDN2 in the single BRI circuit, and causes the monitoring means to monitor the message exchange on the D channel to obtain second Call Appearance information.
 10. A PBX device according to claim 9 wherein said repeating means is coupled to said capture means and causes said capture means to obtain said second Call Appearance information from the D channel.
 11. A PBX device according to claim 10 wherein said repeating means causes said holding means, said dialing means and said monitoring means to repeat the steps of putting a call on hold, generating another call, and monitoring the D channel until the generated call results in a busy signal.
 12. A PBX device according to claim 11 wherein said repeating means causes said dialing means, said holding means and said monitoring means to repeat the steps of generating a call, monitoring the D channel, putting a call on hold, generating another call, and monitoring the D channel until the generated call results in a busy signal with calls being generated from PDN2 to PDN1.
 13. A PBX device according to claim 7 wherein said dialing means and said monitoring means are embodied in a microprocessor with an associated software program.
 14. A PBX device according to claim 7 wherein said dialing means and said monitoring means are embodied in a field programmable gate array.
 15. A PBX device according to claim 7 wherein said dialing means and said monitoring means are embodied in an application specific integrated circuit.
 16. A PBX device according to claim 7 wherein said dialing means and said monitoring means are embodied in firmware in the PBX device.
 17. A PBX device according to claim 9 wherein said dialing means, said monitoring means, said capture means, said holding means, and said repeating means are embodied in a microprocessor with an associated software program.
 18. A PBX device according to claim 9 wherein said dialing means, said monitoring means, said capture means, said holding means, and said repeating means are embodied in a field programmable gate array.
 19. A PBX device according to claim 9 wherein said dialing means, said monitoring means, said capture means, said holding meant, and said repeating means are embodied in an application specific integrated circuit.
 20. A PBX device according to claim 9 wherein said dialing means, said monitoring means, said capture means, said holding means, and said repeating means are embodied in firmware in the PBX device. 